Electrocatalytic alcohol oxidation by a molecular iron complex.

Area of Science:

• Green Chemistry
• Electrochemistry
• Biomimetic Catalysis

Background:

• Selective alcohol oxidation is crucial in organic synthesis.
• Developing sustainable and efficient oxidation methods remains a challenge.
• Electrochemical methods offer a promising alternative to traditional oxidants.

Purpose of the Study:

• To develop an efficient electrochemical method for alcohol oxidation to aldehydes/ketones.
• To utilize a biomimetic iron complex as a redox mediator.
• To employ water as an oxygen source in an undivided electrochemical cell.

Main Methods:

• Electrochemical oxidation using a biomimetic iron complex [(bTAML)Fe^III-OH₂]^-.
• Utilized inexpensive carbon and nickel electrodes.
• Employed water as the oxygen source.
• Investigated substrate scope including heteroatom-containing alcohols.
• Performed mechanistic studies including electrokinetics, LFER, and radical clocks.

Main Results:

• Achieved selective oxidation of alcohols to aldehydes/ketones.
• Demonstrated substrate scope tolerance for O and N heteroatoms.
• Identified a high-valent Fe^V(O) species as the active intermediate via PCET.
• Determined C-H bond oxidation by Fe^V(O) as the rate-determining step.
• Elucidated a
• net hydride
• transfer mechanism.
• Showed potential reduction at higher pH (>11) involving a Fe^IV(O) species.

Conclusions:

• Developed an efficient and selective electrochemical alcohol oxidation.
• The method is sustainable, using water and inexpensive electrodes.
• Mechanistic insights reveal a high-valent iron-oxo species mediating the oxidation via net hydride transfer.